This invention relates to an improved appliance utilized for the cleansing and/or chemical sterilization or disinfecting of small articles such as soft contact lenses.
In recent years extremely soft contact lenses have been fabricated from pliable plastic material which allow extended wear without discomfort. These plastics are hydrophilic, and for that reason contact lenses manufactured from this material are susceptible to contamination by microorganisms. Additionally, as is common with all contact lenses, during use these soft contact lenses develop a natural build-up of proteinaceous material, however, this build-up is worsened by the extended wear of these lenses. Consequently, the user of these lenses must not only disinfect and/or sterilize the lenses, generally on a daily basis to remove the build up of microorganisms, but also effect a cleaning to remove the build-up of proteinaceous material. Failure to properly clean the lenses may lead to congestion of the lens pores causing clouding of the lenses resulting in reduced visibility. Failure to disinfect or sterilize the lenses can lead to infections of the eye.
Various disinfecting techniques are used which heat the lenses in a closed vessel in the presence of a saline solution, the heat being of such intensity and duration as to destroy the contaminating microorganism. More recently, however, sterilizing processes have been developed that do not require heating. These processes utilize a bactericide, for example hydrogen peroxide, which destroys the bacteria on the lenses. In this "cold sterilization" type process, the lenses are immersed in a weak solution of hydrogen peroxide, generally a 3% solution, for several hours. While hydrogen peroxide is an effective bactericide, it is also capable of causing discomfort or injury to a wearer's eye. Therefore, in order to convert the hydrogen peroxide to a benign substance after sterilization is attained, a platinum catalyst is placed in contact with the solution to hasten the decomposition of the hydrogen peroxide, which decomposes to water and oxygen gas.
A problem with this disinfecting process is that if a bactericide such as hydrogen peroxide is used, care must be taken to preclude the possibility of discomfort or injury to the wearer's eye by sufficiently neutralizing the disinfecting agent. Accordingly, the lenses are kept in the bactericide solution for a sufficient length of time to destroy all of the bacteria, after which the lenses may be introduced into a rinsing solution to rinse out excess bactericide. Several hours is generally required to destroy essentially all of the bacteria and neutralize the hydrogen peroxide.
A problem encountered with the foregoing process is that the liberated oxygen gas results in a buildup of gas pressure within the sterilizing chamber and tends to cause leaking, spillage or both upon opening the chamber or when the cap of the unit is not sealed properly. In this regard, when the hydrogen peroxide is brought into contact with the platinum catalyst, the hydrogen peroxide solution tends to break down into water and liberated oxygen gas. The build up of liberated oxygen within the vessel creates pressure which must be vented.
To overcome the problem of cleaning the lenses of the proteinaceous material, certain protein destroying enzymes also have been added to the sterilizing solution. As these enzymes work, the enzymes and the proteinaceous material result in small particles being held in suspension with the liberated oxygen gas that must be vented. Thus a venting system is needed which not only vents the liberated oxygen gas, but can do so and also accommodate the small particles carried by said gases. Further, this must be done in a manner which maintains the sterile integrity of the lens case; that is, prevents the entry of bacteria into the case from the external environment.
In U.S. Pat. No. 4,011,941, there is shown and described a contact lens sterilizer for use with hydrogen peroxide and in which the oxygen gas pressure is relieved by displacing a rubber O-ring. Thus, the O-ring normally seals the unit, but also functions as a check valve. However, when the valve is "open", there is still the possibility of solution leaking therethrough. Moreover, an O-ring can lose resiliency over a period of time causing improper or ineffective valve operation. Further, the O-ring does not readily conform to irregularities in the seating structure and can become displaced leaving small openings through which bacteria may enter.
Additionally, the small particles of the proteinaceous material and other matter removed from the contact lenses are carried by the exhaust gas out of the lens case. When gas is exhausted there is a tendency for proteinaceous material and other particles to be deposited and build up on the valve seating area, thereby creating irregularities which increase the likelihood of bacteria propagation. Not only does the O-ring valve not conform to irregularities due to the deposits on the valve, but it is also incapable of removing these deposits. Thus, over a period of time, the O-ring type vent valve is rendered useless since it does not have means to remove built up deposits.
In U.S. Pat. No. 4,637,919, which is incorporated herein by reference, an appliance is described for disinfecting contact lenses or the like which employs a hydrophobic membrane filter that continuously vents the buildup of gas within the unit during the disinfecting process, while at the same time keeping the unit effectively sealed against leakage of disinfecting solution and entrance of bacteria into the sterilizing chamber. The membrane filter, while effective in venting oxygen gas and preventing the entry of bacteria, is susceptible to clogging when the sterilization solution includes enzymes for cleaning the lenses. The small particles carried by the liberated oxygen gas will be deposited upon the membrane during venting, and the membrane will soon become blocked and cease to function as a vent.
The present invention, as will be detailed more fully hereinafter, overcomes the above described problem. More specifically, the present invention provides an improved venting system that permits oxygen gas to be vented, is not susceptible to clogging, and prevents the entry of bacteria from the exterior of the lens case.